Method and apparatus for hierarchical codebook design in wireless communication

ABSTRACT

A method for use in a multi-user, multi-input multi-output (MU-MIMO) system includes generating a family of codebooks comprising at least one codebook set, the codebook set comprising a plurality of codebooks organized base on a transmission rank and providing the family of codebooks for use in a multiple description coding (MDC) channel feedback scheme.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication Ser. No. 61/257,420 entitled “METHOD AND APPARATUS FORHIERARCHICAL CODEBOOK DESIGN USED IN WIRELESS COMMUNICATION SYSTEM”filed Nov. 2, 2009. The entirety of the aforementioned application isherein incorporated by reference.

BACKGROUND

I. Field of the Invention

The present disclosure relates generally to communication, and morespecifically to techniques for generating and using codebooks in awireless communication system.

II. Background

Wireless communication systems are widely deployed to provide variouscommunication content such as voice, video, packet data, messaging,broadcast, etc. These wireless systems may be multiple-access systemscapable of supporting multiple users by sharing the available systemresources. Examples of such multiple-access systems include CodeDivision Multiple Access (CDMA) systems, Time Division Multiple Access(TDMA) systems, Frequency Division Multiple Access (FDMA) systems,Orthogonal FDMA (OFDMA) systems, and Single-Carrier FDMA (SC-FDMA)systems.

Generally, a wireless multiple-access communication system cansimultaneously support communication for multiple wireless terminals.Each terminal communicates with one or more base stations viatransmissions on the forward and reverse links. The forward link (ordownlink) refers to the communication link from the base stations to theterminals, and the reverse link (or uplink) refers to the communicationlink from the terminals to the base stations. This communication linkmay be established via a single-in-single-out, multiple-in-signal-out ora multiple-in-multiple-out (MIMO) system.

A MIMO system employs multiple (N_(T)) transmit antennas and multiple(N_(R)) receive antennas for data transmission. A MIMO channel formed bythe N_(T) transmit and N_(R) receive antennas may be decomposed intoN_(S) independent channels, which are also referred to as spatialchannels, where N_(S)≦min{N_(T), N_(R)}. Each of the N_(S) independentchannels corresponds to a dimension. The MIMO system can provideimproved performance (e.g., higher throughput and/or greaterreliability) if the additional dimensionalities created by the multipletransmit and receive antennas are utilized.

A MIMO system may support a time division duplex (TDD) and frequencydivision duplex (FDD) systems. In a TDD system, the forward and reverselink transmissions are on the same frequency region so that thereciprocity principle allows the estimation of the forward link channelfrom the reverse link channel. This enables the access point to extracttransmit beamforming gain on the forward link when multiple antennas areavailable at the access point. The beamforming may be achieved byprecoding data prior to transmission. The precoding may be performed ata transmitter using a precoding matrix from a codebook. The codebook isknown to both the transmitter and the intended receiver. In certainoperational conditions, it may be desirable to change or update theprecoding matrix used for transmission from time to time. To facilitatethe selection of an appropriate precoding matrix, a receiver may providefeedback regarding channel conditions. In a system with multipletransmit antennas and multiple ranks of transmission, such as amulti-user MIMO (MU-MIMO) system, the feedback in the uplink directionmay require greater bandwidth than conventional systems.

Better methods for generating codebooks and providing channel conditionfeedback in a MIMO wireless communication systems are needed.

SUMMARY

The systems and methods provided in this disclosure meet the abovediscussed needs, and others. Briefly and in general terms, the discloseddesigns provide methods and apparatuses for generating hierarchicalcodebooks based on transmission ranks, and using the hierarchicalcodebooks in a multiple description coding (MDC) feedback scheme.

In an aspect, a method for wireless communications is provided. Themethod includes generating a family of codebooks comprising at least onecodebook set, the codebook set comprising a plurality of codebooksorganized base on a transmission rank; and providing the family ofcodebooks for use in a multiple description coding (MDC) channelfeedback scheme.

In another aspect, an apparatus for wireless communication is provided.The apparatus includes means for generating a family of codebookscomprising at least one codebook set, the codebook set comprising aplurality of codebooks organized base on a transmission rank; and meansfor providing the family of codebooks for use in a multiple descriptioncoding (MDC) channel feedback scheme.

In yet another aspect, a computer program product is provided whichincludes a computer-readable storage medium. The computer-readablestorage medium comprises instructions for causing at least one computerto generate a family of codebooks comprising at least one codebook set,the codebook set comprising a plurality of codebooks organized base on atransmission rank; and instructions for causing the at least onecomputer to provide the family of codebooks for use in a multipledescription coding (MDC) channel feedback scheme.

In a further aspect, an apparatus for wireless communication isprovided. The apparatus includes a processor configured for: generatinga family of codebooks comprising at least one codebook set, the codebookset comprising a plurality of codebooks organized base on a transmissionrank; and providing the family of codebooks for use in a multipledescription coding (MDC) channel feedback scheme.

In another aspect, a method for wireless communication is provided. Themethod includes receiving a plurality of channel quality reports from auser equipment (UE), according to a multiple description coding (MDC)schedule; and determining a transmission parameter based on theplurality of channel quality reports.

In yet another aspect, an apparatus for wireless communication isprovided. The apparatus includes, comprising means for receiving aplurality of channel quality reports from a user equipment (UE),according to a multiple description coding (MDC) schedule; and means fordetermining a transmission parameter based on the plurality of channelquality reports.

In a further aspect, a computer program product comprising acomputer-readable storage medium is provided. The computer-readablestorage medium includes instructions for causing at least one computerto receive a plurality of channel quality reports from a user equipment(UE), according to a multiple description coding (MDC) schedule; andinstructions for causing the at least one computer to determine atransmission parameter based on the plurality of channel qualityreports.

In another aspect, an apparatus for wireless communication is provided.The apparatus includes a processor configured for: receiving a pluralityof channel quality reports from a user equipment (UE), according to amultiple description coding (MDC) schedule; and determining atransmission parameter based on the plurality of channel qualityreports.

In yet another aspect, a wireless communication method is provided. Themethod includes receiving a family of codebooks organized based on atransmission rank; and reporting, using a multiple description coding(MDC) scheme, a channel quality parameter using a codebook entry fromthe family of codebooks.

In further aspect, a wireless communication apparatus is provided. Theapparatus includes means for receiving a family of codebooks organizedbased on a transmission rank; and means for reporting, using a multipledescription coding (MDC) scheme, a channel quality parameter using acodebook entry from the family of codebooks.

In another aspect, a computer program product comprising acomputer-readable storage medium is provided. The computer-readablestorage medium includes instructions for causing at least one computerto receive a family of codebooks organized based on a transmission rank;and instructions for causing the at least one computer to report, usinga multiple description coding (MDC) scheme, a channel quality parameterusing a codebook entry from the family of codebooks.

In yet another aspect, a wireless communication apparatus is provided.The apparatus includes a processor configured for receiving a family ofcodebooks organized based on a transmission rank; and reporting, using amultiple description coding (MDC) scheme, a channel quality parameterusing a codebook entry from the family of codebooks.

BRIEF DESCRIPTION OF THE DRAWINGS

The features, nature, and advantages of the present disclosure willbecome more apparent from the detailed description set forth below whentaken in conjunction with the drawings in which like referencecharacters identify correspondingly throughout and wherein:

FIG. 1 illustrates a wireless communication system.

FIG. 2 illustrates an exemplary transmission structure.

FIG. 3 illustrates a flow chart representation of a process for wirelesscommunication.

FIG. 4 illustrates a block diagram representation of a portion of anapparatus for wireless communication.

FIG. 5 illustrates a flow chart representation of a process for wirelesscommunication.

FIG. 6 illustrates a block diagram representation of a portion of anapparatus for wireless communication.

FIG. 7 illustrates a flow chart representation of a process for wirelesscommunication.

FIG. 8 illustrates a block diagram representation of a portion of anapparatus for wireless communication.

DESCRIPTION

Various aspects are now described with reference to the drawings. In thefollowing description, for purposes of explanation, numerous specificdetails are set forth in order to provide a thorough understanding ofone or more aspects. It may be evident, however, that the variousaspects may be practiced without these specific details. In otherinstances, well-known structures and devices are shown in block diagramform in order to facilitate describing these aspects.

The techniques described herein may be used for various wirelesscommunication systems such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA and othersystems. The terms “system” and “network” are often usedinterchangeably. A CDMA system may implement a radio technology such asUniversal Terrestrial Radio Access (UTRA), cdma2000, etc. UTRA includesWideband CDMA (WCDMA) and other variants of CDMA. cdma2000 coversIS-2000, IS-95 and IS-856 standards. A TDMA system may implement a radiotechnology such as Global System for Mobile Communications (GSM). AnOFDMA system may implement a radio technology such as Evolved UTRA(E-UTRA), Ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16(WiMAX), IEEE 802.20, Flash-OFDM®, etc. UTRA and E-UTRA are part ofUniversal Mobile Telecommunication System (UMTS). 3GPP Long TermEvolution (LTE) and LTE-Advanced (LTE-A) are new releases of UMTS thatuse E-UTRA, which employs OFDMA on the downlink and SC-FDMA on theuplink. UTRA, E-UTRA, UMTS, LTE, LTE-A and GSM are described indocuments from an organization named “3rd Generation PartnershipProject” (3GPP). cdma2000 and UMB are described in documents from anorganization named “3rd Generation Partnership Project 2” (3GPP2). Thetechniques described herein may be used for the systems and radiotechnologies mentioned above as well as other systems and radiotechnologies. For clarity, certain aspects of the techniques aredescribed below for LTE, and LTE terminology is used in much of thedescription below.

The DL PHY channels may include Physical Downlink Shared Channel(PDSCH), Physical Broadcast Channel (PBSH), Physical Multicast Channel(PMCH), Physical Downlink Control Channel (PDCCH), Physical HybridAutomatic Repeat Request Indicator Channel (PHICH), and Physical ControlFormat Indicator Channel (PCFICH).

The UL PHY Channels may include Physical Random Access Channel (PRACH),Physical Uplink Shared Channel (PUSCH), and Physical Uplink ControlChannel (PUCCH).

Briefly and in general terms, techniques for providing channel qualityfeedback in the uplink direction are disclosed. In one aspect, a familyof codebooks is generated using a hierarchical design. In some designs,the generated codebooks are nested across transmission ranks. In somedesigns, the generated codebooks are hierarchical with respect to thetransmission rank. In one aspect, codebooks are provided to both a basestation and a user equipment (UE) for use during the channel qualityfeedback.

Briefly and in general terms, a technique, called multiple descriptioncoding (MDC) is used to allow fine granular representation of channelconditions. A schedule is provided for using MDC based reporting ofchannel parameters from a UE to a base station. In one aspect, the useof hierarchical or nested codebooks advantageously helps reduce the bitoverhead of reporting channel parameters for different transmissionranks. These and other aspects are further disclosed below.

FIG. 1 shows a wireless communication system 100, which may be an LTEsystem or some other system. System 100 may include a number of evolvedNode Bs (eNBs) 110 and other network entities. An eNB 110 may be anentity that communicates with the UEs and may also be referred to as abase station, a Node B, an access point, etc. Each eNB 110 may providecommunication coverage for a particular geographic area and may supportcommunication for the UEs located within the coverage area. To improvecapacity, the overall coverage area of an eNB may be partitioned intomultiple (e.g., three) smaller areas. Each smaller area may be served bya respective eNB subsystem. In 3GPP, the term “cell” can refer to thesmallest coverage area of an eNB and/or an eNB subsystem serving thiscoverage area.

UEs 120 may be dispersed throughout the system, and each UE 120 may bestationary or mobile. A UE 120 may also be referred to as a mobilestation, a terminal, an access terminal, a subscriber unit, a station,etc. A UE 120 may be a cellular phone, a personal digital assistant(PDA), a wireless modem, a wireless communication device, a handhelddevice, a laptop computer, a cordless phone, a wireless local loop (WLL)station, a smart phone, a netbook, a smartbook, etc.

LTE utilizes orthogonal frequency division multiplexing (OFDM) on thedownlink and single-carrier frequency division multiplexing (SC-FDM) onthe uplink. OFDM and SC-FDM partition a frequency range into multiple(K) orthogonal subcarriers, which are also commonly referred to astones, bins, etc. Each subcarrier may be modulated with data. Ingeneral, modulation symbols are sent in the frequency domain with OFDMand in the time domain with SC-FDM. The spacing between adjacentsubcarriers may be fixed, and the total number of subcarriers (K) may bedependent on the system bandwidth. For example, K may be equal to 128,256, 512, 1024 or 2048 for system bandwidth of 1.25, 2.5, 5, 10 or 20mega-Hertz (MHz), respectively. The system bandwidth may correspond to asubset of the K total subcarriers.

FIG. 2 shows a block diagram of a design of an exemplary basestation/eNB 110 and a UE 120, which may be one of the eNBs and one ofthe UEs in FIG. 1, where the various processes disclosed above may beimplemented, as appropriate. A UE 120 may be equipped with T antennas1234 a through 1234 t, and base station 110 may be equipped with Rantennas 1252 a through 1252 r, where in general T≧1 and R≧1.

At UE 120, a transmit processor 1220 may receive data from a data source1212 and control information from a controller/processor 1240. Transmitprocessor 1220 may process (e.g., encode, interleave, and symbol map)the data and control information and may provide data symbols andcontrol symbols, respectively. Transmit processor 1220 may also generateone or more demodulation reference signals for multiple non-contiguousclusters based on one or more RS sequences assigned to UE 120 and mayprovide reference symbols. A transmit (TX) multiple-inputmultiple-output (MIMO) processor 1230 may perform spatial processing(e.g., precoding) on the data symbols, the control symbols, and/or thereference symbols from transmit processor 1220, if applicable, and mayprovide T output symbol streams to T modulators (MODs) 1232 a through1232 t. Each modulator 1232 may process a respective output symbolstream (e.g., for SC-FDMA, OFDM, etc.) to obtain an output samplestream. Each modulator 1232 may further process (e.g., convert toanalog, amplify, filter, and upconvert) the output sample stream toobtain an uplink signal. T uplink signals from modulators 1232 a through1232 t may be transmitted via T antennas 1234 a through 1234 t,respectively.

At base station 110, antennas 1252 a through 1252 r may receive theuplink signals from UE 120 and provide received signals to demodulators(DEMODs) 1254 a through 1254 r, respectively. Each demodulator 1254 maycondition (e.g., filter, amplify, downconvert, and digitize) arespective received signal to obtain received samples. Each demodulator1254 may further process the received samples to obtain receivedsymbols. A channel processor/MIMO detector 1256 may obtain receivedsymbols from all R demodulators 1254 a through 1254 r. Channel processor1256 may derive a channel estimate for a wireless channel from UE 120 tobase station 110 based on the demodulation reference signals receivedfrom UE 120. MIMO detector 1256 may perform MIMO detection/demodulationon the received symbols based on the channel estimate and may providedetected symbols. A receive processor 1258 may process (e.g., symboldemap, deinterleave, and decode) the detected symbols, provide decodeddata to a data sink 1260, and provide decoded control information to acontroller/processor 1280.

On the downlink, at base station 110, data from a data source 1262 andcontrol information from controller/processor 1280 may be processed by atransmit processor 1264, precoded by a TX MIMO processor 1266 ifapplicable, conditioned by modulators 1254 a through 1254 r, andtransmitted to UE 120. At UE 120, the downlink signals from base station110 may be received by antennas 1234, conditioned by demodulators 1232,processed by a channel estimator/MIMO detector 1236, and furtherprocessed by a receive processor 1238 to obtain the data and controlinformation sent to UE 120. Processor 1238 may provide the decoded datato a data sink 1239 and the decoded control information tocontroller/processor 1240.

Controllers/processors 1240 and 1280 may direct the operation at UE 120and base station 110, respectively. Processor 1220, processor 1240,and/or other processors and modules at UE 120 may perform or directprocesses (e.g., process 700 of FIG. 7) for the techniques describedherein. Processor 1256, processor 1280, and/or other processors andmodules at base station 110 may perform or direct processes (e.g.,process 300 of FIG. 3 and process 500 of FIG. 5) for the techniquesdescribed herein. Memories 1242 and 1282 may store data and programcodes for UE 120 and base station 110, respectively. A scheduler 1284may schedule UEs for downlink and/or uplink transmission and may provideallocations of resources (e.g., assignment of multiple non-contiguousclusters, RS sequences for demodulation reference signals, etc.) for thescheduled UEs.

Different enhancements are being considered in next releases of LTE-A toimprove user experience and system performance. Some example enhancementareas include the introduction of spatial processing techniques such asSU-MIMO with up to 8 layer of transmission, the use of multi-user MIMO(MU-MIMO) configurations and the use of cooperative multipointtransmission (CoMP) to coordinate transmissions by multiple nodes in awireless network.

To support different spatial processing techniques in an efficientmanner, new feedback mechanisms, control signaling and reference signalsare disclosed herein. In some designs, new feedback mechanisms provideinformation about the spatial structure of the channel and the channelquality, and rank (CQI/RI) to the scheduler (e.g., the eNB 110). Theinformation communicated back by a receiver (e.g., the UE 120) to atransmitter (e.g., the eNB 110) is referred herein as “channelstructure” or “channel parameters.” It is to be understood that theterms “channel structure” or “channel parameter” refer to the feedbackprovided by a receiver (e.g., UE 120) to the transmitter (e.g., eNB 110)to facilitate optimized transmission from the transmitter to thereceiver.

For example, in some designs, channel parameters may include a channelquality index (CQI), an estimated rank for transmission, and so on. TheeNB 110 may use the received channel structure information (or channelparameters) to “optimize” transmissions from the eNB 110 to the UE 120.The term “optimization” may refer to transmission improvements such asusing a particular precoding matrix for beamforming, or selecting aparticular rank for transmissions or increased the reliability oftransmission by using error correction codes or increasing noise margin,and so on.

In some designs, a channel spatial structure may be indicated in thefeedback from a receiver to a transmitter by estimating a channel matrixbased on the received signal and by quantizing the channel matrixestimate to the nearest entry in a codebook. One or more codebooks maybe known to both a receiver and a transmitter. Thus, a receiver maysimply indicate to the transmitter which codebook entry to use forsubsequent transmissions. The channel matrix estimate may includeparameters that are continuously variable (i.e., take on a large numberof possible values), but the available number of codebook entries may befinite. Therefore, a receiver may have to decide how to signal acalculated channel matrix using available codebook entries. In otherwords, a receiver may “quantize” channel parameters, when providingfeedback to the transmitter.

In some designs, the codebooks used by the receiver and the transmittermay be changed or updated from time to time. For example, in LTEnetworks, the eNB 110 may update codebooks used by a UE 120 at a startuptime or during run time via higher layer messages. Furthermore,codebooks stored and used at the eNB 110 may also be updated by awireless network operator from time to time, to improve systemperformance

The differences between the actual calculated values and the reportedquantized channel parameters may impact system performance. To minimizesuch quantization errors, various techniques may be utilized forrepresenting channel parameters using a finite number of codebookentries. For example, in some designs, scalar quantization of theelements of the channel matrix may be performed. In a scalarquantization technique, reported values may be chosen on a parameter byparameter basis, from corresponding available values in a codebook.

In some designs, vector quantization may be performed. In a vectorquantization technique, a “nearest” vector entry from a codebook may beselected to feed back a channel parameter vector (e.g., an eigenvectorfor beamforming) based on a predefined metric such as a chordaldistance, or capacity calculation for reporting back to the transmitter.

In some designs, codebooks structures with different sizes may be usedto reduce quantization errors. The size of the codebook (i.e., thenumber of possible entries) used may help improve the accuracy of thefeedback by allowing a more granular representation of calculatedchannel parameter values.

In some designs, the amount of bandwidth needed to report channelparameters from a receiver to a transmitter (e.g., from the UE 120 tothe eNB 110) may be reduced by employing a variety of feedback encodingand compression techniques. For example, in certain designs, feedbackinformation regarding only a single dominant eigen-component (or a firstcertain number of dominant eigen-components) of the channel may be fedback from the UE 120 to the eNB 110. In some designs, the UE 120 maycompute eigen-directions of a channel covariance matrix and report acertain pre-determined number (e.g., one or two) of dominanteigen-directions only. There may be hard and soft limits on the numberof eigen-directions fed back based on different criteria and proceduresagreed by eNB 110 and UE 120. For example, in some designs, a maximumupper limit on the number of eigen-vectors may be used. In some designs,the UE 120 may report eigen-vectors that provide better capacity along aparticular beam direction, and so on.

In some designs, the decision process at a UE 120 about whicheigen-directions to report, may also consider eigen-directions not justfor the serving cell of the UE 120, but also for a neighboring cell aswell. Such a scheme may be useful in networks implementing cooperativemultipoint transmission (CoMP) configurations of LTE-A, to avoidinterference between transmissions to/from different eNBs 110.

Additional reduction in the amount of uplink bandwidth required tocommunicate channel parameters and/or to reduce quantization errors inreporting may be achieved by transforming or projecting actual channelmatrix values to another space. For example, in some designs,eigenvectors computed for a whitened channel version of the actualchannel may be communicated to the transmitter. In some designs, thewhitening may be performed with respect to an interference observed fromtransmissions of a non-cooperating cell. In some designs, the channelmay be whitened using a long-term covariance structure of the channel.The UE 120 may calculate the long-term covariance structure, forexample, over several hundreds of subframes. The whitening over a longterm observation window may be particularly useful in configurationswhere transmit antennas are closely spaced or in propagation scenarioswith small angular spread. In some designs, the eigen-vectors may becalculated based on a projection in a particular direction, whichassumes a particular receiver beamforming vector.

Another technique called feedback encoding may also be used to reducethe uplink bandwidth required to report channel parameters from the UE120 to the eNB 110. In a feedback encoding design, data compression,based on channel correlation in time/frequency/space dimensions, may beused to reduce transmission overhead for reporting the channelconditions. Alternatively, channel correlation may be used to improvethe accuracy of the channel knowledge at the scheduler (e.g., the eNB120) in a given amount of upstream bandwidth.

Multiple description coding (MDC) is yet another technique that may beused to reduce quantization errors in reporting channel parameterfeedback from the UE 120 to the eNB 110. Each MDC report may beconsidered to provide a “look” of the channel from a UE's vantage point.The look may, for example, be associated with a time period and/or afrequency band. Broadly speaking, in an MDC scheme, the UE 120 mayprovide the eNB 110 information about various looks of the channel overa period of time and a span of frequency. Correspondingly, the eNB 110may combine the received different looks to derive a better estimate ofreported channel conditions. Combining different reports (or “looks”)may improve the accuracy of channel knowledge at the eNB 110. In otherwords, using MDC, the UE 120 may be able to improve the granularity ofreporting (i.e., reduce the quantization error) of channel conditions.Of course, the eNB 110 is free to combine or not combine receivedchannel feedbacks because each channel feedback may be close to theactual calculated value at a UE 120. In an MDC scheme, codebookstructures may be used to provide different looks of the channel atdifferent time instances and/or frequency bands. Combining reports basedon these codebooks can reduce quantization errors. This, and otheraspects of using codebooks MDC coding are further described below.

To illustrate the MDC coding scheme, assume that a codebook being usedby the UE 120 comprises integer channel parameter values only. In thisscenario, to feed back a channel parameter value “2.5,” in conventionalsystems, a UE 120 may have to make a decision about whether to signalthe desired channel parameter value “2.5” using, entry “2” or entry “3.”However, in an MDC scheme, the UE 120 may alternate (ping pong) betweenvalues “2” and “3.” At the eNB 110, the received values “2” and “3” maybe averaged or lowpass filtered to arrive at the value “2.5” intended bythe UE 120. It will be appreciated that by adjusting the duty cycle ofreported codebook values over a reporting period, it may be possible toreport a large number of intermediate channel parameter values by the UE120. Correspondingly, the eNB 110 may recover these intermediate valuesby averaging over the given MDC reporting period.

When operational conditions are such that the communication channelbetween the eNB 110 and the UE 120 are slowly varying, compared to thetime instances of channel parameter feedback, finer granularity ofsignaled channel parameter values can be achieved using long patterns ofavailable codebook values. For example, when the channel is a widebandLTE channel, frequency domain properties of the channel may not changerapidly, compared to a typical feedback period of 5 to 10 subframes. Insuch a case, ten consecutive channel parameter reports may be averagedto report channel parameter values accurate to the first decimal place(assuming integer codebook entries).

In some designs, MDC codebooks may have an associated predeterminedschedule of transmission. The MDC schedule may facilitate fine granularreporting of channel parameters, such as described above. The MDCschedule may include, for example, information regarding the sequence oftransmission of channel parameters, which codebooks from a set ofcodebooks to use, and how parameter averaging is to be performed.Further details of the MDC scheduling and codebook sets are providedbelow.

In some designs, multiple sets of codebooks may be available for use bya receiver. For example, for the previously discussed example related tosignaling a channel parameter value “2.5” using available codebookentries “2” and “3,” in certain designs, a UE 120 may have two sets ofcodebooks available. A first codebook may allow reporting channelparameter values {1, 2, 3 . . . } while a second codebook may allowreporting half-integer values {0.5, 1.5, 2.5, . . . }. In such a case,to signal channel parameter 2.5, the UE 120 may select eithertransmission of alternating “2” and “3” from the first codebook, aspreviously described, or may directly signal “2.5” from the secondcodebook. The UE's choice of which codebook to use may depend on thescheduling scheme associated with the feedback. It should be emphasizedthat the example codebooks comprising integer and half-integer valuesare for illustrative purposes only. The MDC techniques described hereinare applicable to any type of codebook entries, including rational orirrational values.

In some designs, codebooks may be designed to facilitate channelparameter reporting using low uplink bandwidth and/or reducedquantization error. In some designs, codebook design may be performed apriori and the designed codebooks may be stored at the eNB 110 and theUE 120. The design and generation of codebooks may be performed at acomputer (which may or may not be located at the eNB 110) and then thecodebooks may be communicated to the eNB 110 and/or UE 120 for futureuse. In some designs, the new codebooks may be generated based onobserved channel conditions or a transmission configurations (e.g.,antenna configuration at the eNB 110). In some designs, new codebooksmay be provided to the UE 120 via high level signaling.

In some designs, codebooks may be generated to using a nestedarchitecture. In some nested architecture designs, codebooks may benested across transmission ranks. This property may mean that codebooksused for a lower transmission rank nay be extended to obtain codebooksfor a higher transmission rank. For example, in a nested architecture,rank 1 vectors in codebook for rank 1 are columns of a subset of rank 2matrices present in codebook for rank 2.

In some designs, codebook structures may be designed for different ranksto be compatible with MDC techniques discussed above. In other words,codebooks may be both rank nested and be able to provide reporting withlow quantization errors, using MDC scheduling. It will be appreciatedthat the availability of such codebooks at a UE 120 facilitates an MDCfeedback scheme, including rank selection by the UE 120.

In some designs, a nested structure may be provided for each codebookamong a set of codebooks used by MDC. In other words, a family of nestedcodebook sets, may be defined as follows:

F={S₁,S₂, . . . ,S_(k)}  Eq. (1)

where k is the number of codebook sets in the family F. The family F maybe partitioned as follows. Each S_(i) may be a nested codebook set thatcontains codebooks for rank 1 to the desired rank say r_(i). In otherwords, each S_(i) may be represented as follows:

S_(i)={C_(1,i),C_(2,i), . . . , C_(ri,i)};   Eq. (2)

where C_(j,i) is the codebook for rank j in set i. Variables i, j andr_(i) are integers. At each time/frequency instance, one of the codebooksets S_(i) may be chosen and within that set for different ranks (e.g.j) the C_(j,i) may be used for reporting.

In some designs, codebooks may be designed to have a hierarchicalstructure across transmission ranks. For example, a family of, N₁codebooks, each codebook having M₁-bits, may be defined for rank 1,based on a particular criterion such as inner product metric (N₁ and M₁both integers). Let the family of codebooks be denoted by

F₁={C_(1,1), . . . C_(1,N1)};   Eq. (3)

where each C_(1,j) is of size 2^(M1).

The family F₁ of N₁ codebooks may be partitioned into a smaller numberof families, say N₂ families, i.e. F₂={C_(2,1), C_(2,N2)}. A subset ofthe set of rank 1 vectors in each family can be selected and extended bya particular criterion, e.g. chordal distance, orthogonal component, torank 2 matrices. In this case MDC for rank 1 UEs 120 (i.e., UEs 120 forwhich the transmission channel has rank 1) may use family F₁ of N₁codebooks (of size M₁-bit each). Similarly, for rank 2 UEs, family F₂ ofN₂ codebooks may be used. If all the rank 1 vectors in each family areselected, then codebooks of family F2 will be of size M₁+log₂(N₁/N₂)each. It will be appreciated that the codebooks, as defined above, alsohave a nested structure. This approach can be extended to higher ranksby repeating the process of nesting.

In some design, the nested structure of the codebook families may beobtained by a top-down process starting from the family of codebooks forhigher rank transmission. Let the family of codebooks constructed forhigher rank transmission be F₂={C_(2,1), . . . C_(2,N2)}, C_(2j) is thej-th codebook in the family. In this case, one can first select a subsetof codebooks from F₂, the family of codebooks constructed for higherrank transmission. Let this subset of codebooks be denoted asG={C_(2,i1), . . . C_(2,ik)}. For each codebook in G, subset ofcodebooks chosen, multiple sub-sampled codebooks are generated byselecting a subset of matrices in that codebook and partitioning theminto multiple sub-sampled codebooks. Each of the sub-sampled codebookscan be used as instance of MDC codebook for lower rank transmissions. Itwill be appreciated that the codebooks, as defined above, also have anested structure. This approach can be extended to higher ranks byrepeating the process of nesting.

In general, the size of the codebooks used for different ranks can bedifferent. In some designs, finer granularity codebooks may be providedfor lower ranks (because in typical operational scenarios, lower rankchannel parameters may be used more frequently and may be applicable toall scenarios). Correspondingly, higher rank codebook may be designed tohave smaller sizes than the lower rank codebooks.

In some designs, a codebook design can be configurable and differentcodebooks can be defined and semi-statically assigned for feedbackcomputation to different UEs 120. The choice of the codebook assigned toeach UE 120 may be based on different parameters such as UE channelconditions, e.g. Doppler, angular spread, or network configurations,e.g. Tx antenna configuration, number of UEs and dominant operation mode(SU, MU or CoMP). Furthermore, the assigned codebooks may also depend ontransmission antenna configuration at the eNB 110. For example, when aneNB 110 has linearly spaced antennas, the transmission pattern may beFFT-like and a codebook set generated using rotation of matrices may beused.

In some designs, the family of codebooks used may be selectedsemi-statically for use between UEs 120 and eNB 110. The selection (andchanges to the selected family) may be communicated by the eNB 110 via ahigher layer message. The selection is called semi-static in the sensethat the selection of the family of codebooks used may be kept unchangedover several tens of subframe duration (e.g., over 10 or 100 or 1000subframes).

In some designs, the above-discussed MDC feedback schemes may be used ina tiered manner. In a tiered scheme, for example, channel parameters maybe sent using a conventional feedback scheme. In addition to theconventional feedback scheme, MDC reporting may be used to inform theeNB 110 about deviations to the previously reported channel parameters,reported using a conventional feedback scheme. As previously discussed,MDC techniques facilitate reporting of highly granular values (i.e.,lower quantization errors). Therefore, in one aspect, the tieredtechnique may allow “fine tuning” of reported channel parameters. Forexample, when angular spread of a transmitted beam from the eNB 110 issmall (e.g., 10 degrees or lower), then eigenvector directions used forbeamforming may not change rapidly (e.g., on a subframe by subframebasis). A small beamforming angle may be achieved, for example, whentransmit antennas on the eNB 110 are closely spaced, relative to thewavelength of transmission. A tiered feedback scheme may be used in suchconfigurations.

FIG. 3 is a flow chart showing a process 300 of wireless communicationin a MU-MIMO system. At block 302, a family of codebooks comprising atleast one codebook set, the codebook set comprising a plurality ofcodebooks organized base on a transmission rank, is generated. Thecodebook set comprises a plurality of hierarchical codebooks. Thecodebooks may be generated as described with respect to Eqs. (1) to (3)above. At block 304, the family of codebooks for use in a multipledescription coding (MDC) channel feedback scheme is provided. Aspreviously discussed, the family of codebooks may be organizedhierarchically or in a nested fashion, based on the transmission rank.The codebook generation may be performed at a computer communicativelycoupled to the eNB 110.

In some designs, an MDC schedule is and provided for use with the MDCfeedback scheme. Various possibilities of MDC schedule, e.g., using MDCfor fine granularity refinement, have been discussed herein.Furthermore, the generation of MDC schedule may include generation ofMDC schedule based on transmission configuration of the eNB 110 and/orthe UE 120 and operation conditions such as channel quality.

In some designs, the family of codebooks may be partitioned in aplurality of subfamilies based on the transmission rank, whereincodebooks for transmission ranks greater than one are generated byextending rank 1 codebooks according to a criterion. The transmissioncriterion used for extending from rank 1 codebooks to higher rankcodebooks may include chordal distance or may be based on an orthogonalcomponent method, as previously discussed.

In some designs, the family of codebooks may be partitioned into aplurality of subfamilies, each subfamily comprising codebooks for aplurality of transmission ranks, as previously discussed with respect toEq. (1).

In some designs, as previously discussed, the family of codebooks may begenerated using a random, a Gaussian or a unitary matrix as a startingpoint. In some designs, the family of codebooks may be generated basedon a transmitter configuration such as a number of antennas, theplacement of antennas and so on.

FIG. 4 is a block diagram representation of a portion of a wirelesscommunication apparatus 400 comprising module 402 for generating afamily of codebooks comprising at least one codebook set, the codebookset comprising a plurality of codebooks organized base on a transmissionrank and module 404 for providing the family of codebooks for use in amultiple description coding (MDC) channel feedback scheme. The family ofcodebook may be provided to the eNB 110 and the UE 120 a priori, orduring run time, by sending higher layer messages from the eNB 110 tothe UE 120. The wireless communication device 400 may, for example, be acomputer coupled to the eNB 110. The communication apparatus 400,including modules 402 and 404 may further implement one or more of thepreviously discussed codebook generation techniques for feedbackbandwidth reduction and/or quantization error reduction.

FIG. 5 is a flow chart representation of a process 500 of a method foruse in a wireless communication system. The process 500 may, forexample, be implemented at the eNB 110. At block 502, a first pluralityof channel quality reports are received from a UE 120, according to amultiple description coding (MDC) schedule. At block 504, a transmissionparameter is determined based on the first plurality of channel qualityreports. In some designs, each channel quality report from the firstplurality of channel quality reports comprises an indication of acodebook entry.

In some designs, a second plurality of channel quality reports, notscheduled according to the MDC schedule, is received. The secondplurality of channel quality reports may for example be used todetermine the transmission parameters. In some designs, a first value iscalculated using the first plurality of channel quality reports toadjust a second value calculated using the second plurality of channelquality reports.

FIG. 6 is a block diagram representation of a portion of a wirelesscommunication apparatus 600, comprising module 602 for receiving a firstplurality of channel quality reports from a user equipment (UE),according to a multiple description coding (MDC) schedule and module 604for determining a transmission parameter based on the first plurality ofchannel quality reports. The wireless communication apparatus 600 maybe, for example, the eNB 110. The apparatus 600 and modules 602, 604 mayfurther implement one or more of the techniques for reducing feedbackbandwidth and/or quantization errors using hierarchical codebooks, asdisclosed herein.

FIG. 7 is a flow chart representation of a process 700 of wirelesscommunication. The process 700 may, for example, be implemented at theUE 120. At block 702, a family of codebooks organized based on atransmission rank is received. At block 704, a channel quality parameterusing a codebook entry from the family of codebooks is reported using amultiple description coding (MDC) scheme. In some designs, the channelquality parameter may comprise the desired transmission rank. The familyof codebooks received may be hierarchically organized according totransmission ranks. The codebook entry reported in block 704 may beselected based on the desired transmission rank. In some designs, thefamily of codebooks may be nested according to the transmission ranks.The family of codebooks received may be, for example, as discussed withrespect to Eqs. (1) to (3) above.

FIG. 8 is a block diagram representation of a portion of a wirelesscommunication apparatus 800, comprising module 802 for receiving afamily of codebooks organized based on a transmission rank and module804 for reporting, using a multiple description coding (MDC) scheme, achannel quality parameter using a codebook entry from the family ofcodebooks. The communication apparatus 800, including modules 802 and804 may further implement one or more of the previously discussedcodebook generation techniques for feedback bandwidth reduction and/orquantization error reduction.

In some designs, the channel quality parameter comprises a desiredtransmission rank that the eNB 110 should use when communicating withthe UE 120.

In some designs, the received family of codebooks is hierarchicallyorganized according to transmission ranks and the UE 120 selects acodebook entry corresponding to the desired transmission rank andreports the selected codebook entry to the eNB 110.

It will be appreciated that in the foregoing description, severaltechniques for reducing quantization errors and/or bandwidth overheadassociated with providing channel feedback from a receiver to atransmitter are provided. Techniques have been disclosed for generatingcodebooks. In one aspect, the codebooks may be organized into familiesof codebooks according to the desired transmission rank. In one aspect,the codebooks may be especially usefully in providing channel feedbackusing a multiple description coding (MDC) feedback scheme.

It will further be appreciated that techniques have been disclosed togenerate families of codebooks hierarchically organized according to atransmission rank. In one aspect, the hierarchical arrangement maycomprise a family of N₁ codebooks for rank 1. Codebooks for higherranks, e.g., rank 2, may be generated by extending rank 1 codebooksusing a particular criterion such as minimizing a chordal distancebetween generated matrices or by extending rank 1 matrices alongparticular orthogonal components, etc.

It will further be appreciated that techniques have been disclosed toorganize families of codebooks by nesting based on transmission ranks.In one aspect, a family of codebooks may comprise nested codebook sets,with each codebook set comprising codebooks for ranks 1 through rl(where rl is an integer greater than 1).

It will further be appreciated that the codebook families may be usedfor channel parameter feedback using an MDC scheme. It will beappreciated that the combination of MDC and codebooks nested accordingto transmission ranks provides previously unobtainable savings in uplinkbandwidth overhead and/or reduction in quantization error, while stillallowing a UE 120 to provide feedback based on a desired transmissionrank for transmissions from the eNB 110 to the UE 120.

Those of skill in the art would understand that information and signalsmay be represented using any of a variety of different technologies andtechniques. For example, data, instructions, commands, information,signals, bits, symbols, and chips that may be referenced throughout theabove description may be represented by voltages, currents,electromagnetic waves, magnetic fields or particles, optical fields orparticles, or any combination thereof.

Those of skill would further appreciate that the various illustrativelogical blocks, modules, circuits, and process steps described inconnection with the disclosure herein may be implemented as electronichardware, computer software, or combinations of both. To clearlyillustrate this interchangeability of hardware and software, variousillustrative components, blocks, modules, circuits, and steps have beendescribed above generally in terms of their functionality. Whether suchfunctionality is implemented as hardware or software depends upon theparticular application and design constraints imposed on the overallsystem. Skilled artisans may implement the described functionality invarying ways for each particular application, but such implementationdecisions should not be interpreted as causing a departure from thescope of the present disclosure.

The various illustrative logical blocks, modules, and circuits describedin connection with the disclosure herein may be implemented or performedwith a general-purpose processor, a digital signal processor (DSP), anapplication specific integrated circuit (ASIC), a field programmablegate array (FPGA) or other programmable logic device, discrete gate ortransistor logic, discrete hardware components, or any combinationthereof designed to perform the functions described herein. Ageneral-purpose processor may be a microprocessor, but in thealternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

The steps of a method or algorithm described in connection with thedisclosure herein may be embodied directly in hardware, in a softwaremodule executed by a processor, or in a combination of the two. Asoftware module may reside in RAM memory, flash memory, ROM memory,EPROM memory, EEPROM memory, registers, hard disk, a removable disk, aCD-ROM, or any other form of storage medium known in the art. Anexemplary storage medium is coupled to the processor such that theprocessor can read information from, and write information to, thestorage medium. In the alternative, the storage medium may be integralto the processor. The processor and the storage medium may reside in anASIC. The ASIC may reside in a user terminal. In the alternative, theprocessor and the storage medium may reside as discrete components in auser terminal.

In one or more exemplary designs, the functions described may beimplemented in hardware, software, firmware, or any combination thereof.If implemented in software, the functions may be stored on ortransmitted over as one or more instructions or code on acomputer-readable medium. Computer-readable media includes both computerstorage media and communication media including any medium thatfacilitates transfer of a computer program from one place to another. Astorage media may be any available media that can be accessed by ageneral purpose or special purpose computer. By way of example, and notlimitation, such computer-readable media can comprise RAM, ROM, EEPROM,CD-ROM or other optical disk storage, magnetic disk storage or othermagnetic storage devices, or any other medium that can be used to carryor store desired program code means in the form of instructions or datastructures and that can be accessed by a general-purpose orspecial-purpose computer, or a general-purpose or special-purposeprocessor. Disk and disc, as used herein, includes compact disc (CD),laser disc, optical disc, digital versatile disc (DVD), floppy disk andblu-ray disc where disks usually reproduce data magnetically, whilediscs reproduce data optically with lasers. Combinations of the aboveshould also be included within the scope of computer-readable media.

The previous description of the disclosure is provided to enable anyperson skilled in the art to make or use the disclosure. Variousmodifications to the disclosure will be readily apparent to thoseskilled in the art, and the generic principles defined herein may beapplied to other variations without departing from the spirit or scopeof the disclosure. Thus, the disclosure is not intended to be limited tothe examples and designs described herein but is to be accorded thewidest scope consistent with the principles and novel features disclosedherein.

In view of the exemplary systems described supra, methodologies that maybe implemented in accordance with the disclosed subject matter have beendescribed with reference to several flow diagrams. While for purposes ofsimplicity of explanation, the methodologies are shown and described asa series of blocks, it is to be understood and appreciated that theclaimed subject matter is not limited by the order of the blocks, assome blocks may occur in different orders and/or concurrently with otherblocks from what is depicted and described herein. Moreover, not allillustrated blocks may be required to implement the methodologiesdescribed herein. Additionally, it should be further appreciated thatthe methodologies disclosed herein are capable of being stored on anarticle of manufacture to facilitate transporting and transferring suchmethodologies to computers. The term article of manufacture, as usedherein, is intended to encompass a computer program accessible from anycomputer-readable device, carrier, or media.

It should be appreciated that any patent, publication, or otherdisclosure material, in whole or in part, that is said to beincorporated by reference herein is incorporated herein only to theextent that the incorporated material does not conflict with existingdefinitions, statements, or other disclosure material set forth in thisdisclosure. As such, and to the extent necessary, the disclosure asexplicitly set forth herein supersedes any conflicting materialincorporated herein by reference. Any material, or portion thereof, thatis said to be incorporated by reference herein, but which conflicts withexisting definitions, statements, or other disclosure material set forthherein, will only be incorporated to the extent that no conflict arisesbetween that incorporated material and the existing disclosure material.

1. A method for wireless communication, comprising: generating a familyof codebooks comprising at least one codebook set, the codebook setcomprising a plurality of codebooks organized base on a transmissionrank; and providing the family of codebooks for use in a multipledescription coding (MDC) channel feedback scheme.
 2. The method of claim1, wherein the plurality of codebooks are organized hierarchically basedon the transmission rank.
 3. The method of claim 2, further comprising:subsampling codebooks of a family of codebooks; and partitioning thesubsampled codebooks into a plurality of subfamilies based on thetransmission rank, wherein codebooks for transmission ranks greater thanone are generated by extending rank 1 codebooks according to acriterion.
 4. The method of claim 3, wherein the extending is based onone of a chordal distance and an orthogonal component method.
 5. Themethod of claim 1, wherein the plurality of codebooks are nested basedon the transmission rank.
 6. The method of claim 5, further comprisingpartitioning the family of codebooks into a plurality of subfamilies,each subfamily comprising codebooks for a plurality of transmissionranks.
 7. The method of claim 5, wherein the nested structure of theplurality of codebooks based on transmission ranks is obtained by:selecting a set of sub-matrices from matrices in codebooks for a firsttransmission rank family; selecting a subset of the selectedsub-matrices; and partitioning the selected subset of sub-matrices intomultiple codebooks used for a second transmission rank; wherein thesecond transmission rank is less than the first transmission rank. 8.The method of claim 5, further comprising generating a first family ofcodebooks for a maximum possible rank; selecting a subset of codebooksin the first family; and generating multiple codebooks for lower ranktransmissions by sub-sampling matrices of the selected subset ofcodebooks in the first family.
 9. The method of claim 1, furthercomprising providing a schedule for the MDC channel feedback scheme. 10.The method of claim 1, wherein the generating the family of codebookscomprises generating the family of codebooks by using one of random,Gaussian and unitary matrices.
 11. The method of claim 1, wherein thegenerating the family of codebooks comprises generating the family ofcodebooks from a given codebook and different unitary transformations onthe given codebook.
 12. The method of claim 1, wherein the generatingthe family of codebooks comprises generating the family of codebooksbased on a transmitter configuration.
 13. An apparatus for wirelesscommunication, comprising: means for generating a family of codebookscomprising at least one codebook set, the codebook set comprising aplurality of codebooks organized base on a transmission rank; and meansfor providing the family of codebooks for use in a multiple descriptioncoding (MDC) channel feedback scheme.
 14. The apparatus of claim 13,wherein the plurality of codebooks are organized hierarchically based onthe transmission rank.
 15. The apparatus of claim 14, furthercomprising: means for subsampling codebooks of a family of codebooks;and means for partitioning the subsampled codebooks into a plurality ofsubfamilies based on the transmission rank, wherein codebooks fortransmission ranks greater than one are generated by extending rank 1codebooks according to a criterion.
 16. The apparatus of claim 15,wherein the extending is based on one of a chordal distance and anorthogonal component method.
 17. The apparatus of claim 13, wherein theplurality of codebooks are nested based on the transmission rank. 18.The apparatus of claim 17, further comprising means for partitioning thefamily of codebooks in a plurality of subfamilies, each subfamilycomprising codebooks for a plurality of transmission ranks.
 19. Theapparatus of claim 17, wherein the nested structure of the plurality ofcodebooks based on transmission ranks is obtained by: means forselecting a set of sub-matrices from matrices in codebooks for a firsttransmission rank family; means for selecting a subset of the selectedsub-matrices; and means for partitioning the selected subset ofsub-matrices into multiple codebooks used for a second transmissionrank; wherein the second transmission rank is less than the firsttransmission rank.
 20. The apparatus of claim 17, further comprising:means for generating a first family of codebooks for the maximumpossible rank; means selecting a subset of codebooks in the firstfamily; and means for generating multiple codebooks for lower ranktransmissions by sub-sampling matrices of the selected subset ofcodebooks in the first family.
 21. The apparatus of claim 13, furthercomprising means for providing a schedule for the MDC channel feedbackscheme.
 22. The apparatus of claim 13, wherein the means for generatingthe family of codebooks comprises means for generating the family ofcodebooks by using one of random, Gaussian and unitary matrices.
 23. Theapparatus of claim 13, wherein the means for generating the family ofcodebooks comprises means for generating the family of codebooks from agiven codebook and different unitary transformations on the givencodebook.
 24. The apparatus of claim 13, wherein the means forgenerating the family of codebooks comprises means for generating thefamily of codebooks based on a transmitter configuration.
 25. A computerprogram product comprising a computer-readable storage medium, thecomputer-readable storage medium comprising: instructions for causing atleast one computer to generate a family of codebooks comprising at leastone codebook set, the codebook set comprising a plurality of codebooksorganized base on a transmission rank; and instructions for causing theat least one computer to provide the family of codebooks for use in amultiple description coding (MDC) channel feedback scheme.
 26. Thecomputer program product of claim 25, wherein the plurality of codebooksare organized hierarchically based on the transmission rank.
 27. Anapparatus for wireless communication, comprising: a processor configuredfor: generating a family of codebooks comprising at least one codebookset, the codebook set comprising a plurality of codebooks organized baseon a transmission rank; and providing the family of codebooks for use ina multiple description coding (MDC) channel feedback scheme.
 28. Theapparatus of claim 27, wherein the plurality of codebooks are organizedhierarchically based on the transmission rank.
 29. A method for wirelesscommunication, comprising: receiving a plurality of channel qualityreports from a user equipment (UE), according to a multiple descriptioncoding (MDC) schedule; and determining a transmission parameter based onthe plurality of channel quality reports.
 30. The method of claim 29,wherein each channel quality report from the plurality of channelquality reports comprises an indication of a codebook entry.
 31. Themethod of claim 29, further comprising receiving another plurality ofchannel quality reports not scheduled according to an MDC schedule. 32.The method of claim 31, wherein the determining the transmissionparameter comprises using a first value calculated using the pluralityof channel quality reports to adjust a second value calculated using theanother plurality of channel quality reports.
 33. An apparatus forwireless communication, comprising: means for receiving a plurality ofchannel quality reports from a user equipment (UE), according to amultiple description coding (MDC) schedule; and means for determining atransmission parameter based on the plurality of channel qualityreports.
 34. The apparatus of claim 33, wherein each channel qualityreport from the plurality of channel quality reports comprises anindication of a codebook entry.
 35. The apparatus of claim 34, furthercomprising means for receiving another plurality of channel qualityreports not scheduled according to an MDC schedule.
 36. The apparatus ofclaim 35, wherein the means for determining the transmission parametercomprises means for using a first value calculated using the pluralityof channel quality reports to adjust a second value calculated using theanother plurality of channel quality reports.
 37. A computer programproduct comprising a computer-readable storage medium, thecomputer-readable storage medium comprising: instructions for causing atleast one computer to receive a plurality of channel quality reportsfrom a user equipment (UE), according to a multiple description coding(MDC) schedule; and instructions for causing the at least one computerto determine a transmission parameter based on the plurality of channelquality reports.
 38. An apparatus for wireless communication,comprising: a processor configured for: receiving a plurality of channelquality reports from a user equipment (UE), according to a multipledescription coding (MDC) schedule; and determining a transmissionparameter based on the plurality of channel quality reports.
 39. Awireless communication method, comprising: receiving a family ofcodebooks organized based on a transmission rank; and reporting, using amultiple description coding (MDC) scheme, a channel quality parameterusing a codebook entry from the family of codebooks.
 40. The method ofclaim 39, wherein the channel quality parameter comprises a desiredtransmission rank.
 41. The method of claim 40, wherein the family ofcodebooks is hierarchically organized according to transmission ranksand the codebook entry is selected based on the desired transmissionrank.
 42. The method of claim 40, wherein the family of codebooks isnested according to transmission ranks and the codebook entry isselected based on the desired transmission rank.
 43. A wirelesscommunication apparatus, comprising: means for receiving a family ofcodebooks organized based on a transmission rank; and means forreporting, using a multiple description coding (MDC) scheme, a channelquality parameter using a codebook entry from the family of codebooks.44. The apparatus of claim 43, wherein the channel quality parametercomprises a desired transmission rank.
 45. The apparatus of claim 44,wherein the family of codebooks is hierarchically organized according totransmission ranks and the codebook entry is selected based on thedesired transmission rank.
 46. The apparatus of claim 44, wherein thefamily of codebooks is nested according to transmission ranks and thecodebook entry is selected based on the desired transmission rank.
 47. Acomputer program product comprising a computer-readable storage medium,the computer-readable storage medium comprising: instructions forcausing at least one computer to receive a family of codebooks organizedbased on a transmission rank; and instructions for causing the at leastone computer to report, using a multiple description coding (MDC)scheme, a channel quality parameter using a codebook entry from thefamily of codebooks.
 48. The computer program product of claim 47,wherein the channel quality parameter comprises a desired transmissionrank; wherein the family of codebooks is one of hierarchically organizedaccording to transmission ranks and nested according to transmissionranks; wherein the codebook entry is selected based on the desiredtransmission rank.
 49. A wireless communication apparatus comprising: aprocessor configured for: receiving a family of codebooks organizedbased on a transmission rank; and reporting, using a multipledescription coding (MDC) scheme, a channel quality parameter using acodebook entry from the family of codebooks.
 50. The apparatus of claim49, wherein the channel quality parameter comprises a desiredtransmission rank; wherein the family of codebooks is one ofhierarchically organized according to transmission ranks and nestedaccording to transmission ranks; wherein the codebook entry is selectedbased on the desired transmission rank.